Cheers for the input guys, i have some decisive info about this whole thing:
I just got back from my engine builder, i took out all plugs etc, cylinder 3 and 4 plugs were a little wet around the bottom of the threads, 4th plug was blacker than all the others, others were fine.
Anyways we chucked the camera down all the plug holes and found that all the bores are completely glazed, i saw for myself they look like chrome, no hone marks whatsoever.
The outer circumference of the 4th piston is clean as a whistle, the rest of it carbon, it seems this ring isnt sealing, and 3rd not as bad but still clean. Im thinking the others wont be far away. We had 4th piston up, cranked it down and we saw oil sitting at the top of the bore, it started running down the bore.
We also checked the valve stems while they were open, there was no oil on any of the stems.
My car has always blown a fair bit of black shit since the tune (never revved it over 4k or flat stick before the tune), but i didnt think anything of it because i thought it was right.
What the f**k has caused this to happen to my engine??